AQA · GCSE · Biology

    Course version: 8461 · Version from Sept 2018

    The products of digestion are used to build new carbohydrates, lipids and…

    Full specification wording

    The human digestive system: The products of digestion are used to build new carbohydrates, lipids and proteins. Some glucose is used in respiration.

    The products of digestion are absorbed into the blood and used by cells.

    Checked against the AQA 8461 specification (opens in a new tab) on .

    • Point 13 of 25
    • 4 key terms

    Study notes

    From the checked teaching notes for this specification point.

    The idea

    The products of digestion are absorbed into the blood and used by cells. Simple sugars such as glucose are used to build new carbohydrates, including glycogen, and some glucose is used in respiration to release energy. Amino acids are used to build new proteins, such as enzymes, hormones and structural proteins. Glycerol and fatty acids are used to build new lipids, including cell membranes and energy stores. These processes are examples of synthesis, and they require energy.

    What earns the marks

    • The products of digestion are absorbed into the blood, mainly in the small intestine.
    • Simple sugars such as glucose are used to build new carbohydrates, including glycogen.
    • Some glucose is used in respiration to release energy for cells.
    • Amino acids are used to build new proteins, such as enzymes and structural proteins.
    • Glycerol and fatty acids are used to build new lipids, including cell membranes and energy stores.
    • Synthesis of new biological molecules requires energy from respiration.

    Common mistakes and how to put them right

    • Saying all glucose is used only in respiration.

      Put it right: Some glucose is used to build new carbohydrates, and some is used in respiration.

    • Saying amino acids are used to build carbohydrates.

      Put it right: Amino acids are used to build proteins.

    • Forgetting that glycerol and fatty acids are used to build lipids.

      Put it right: They are used to build new lipids such as cell membranes.

    Exam tips

    • Link each product of digestion to its use: glucose to carbohydrates and respiration, amino acids to proteins, glycerol and fatty acids to lipids.
    • Mention absorption in the small intestine and transport by the blood.
    • Use the term synthesis when describing how products are used to build new molecules.

    Try the lesson

    The start of the The human digestive system: The products of digestion are used to build new carbohydrates, lipids and proteins. Some glucose is used in respiration. lesson, made from checked teaching notes for this specification point.

    Have a go first

    After digestion, glucose is absorbed into the bloodstream and transported to cells. What is a primary use of this glucose in the human body?

    Listen

    The products of digestion are absorbed into the blood and used by cells. Simple sugars such as glucose are used to build new carbohydrates, including glycogen, and some glucose is used in respiration to release energy. Amino acids are used to build new proteins, such as enzymes, hormones and structural proteins. Glycerol and fatty acids are used to build new lipids, including cell membranes and energy stores. These processes are examples of synthesis, and they require energy. A strong answer earns marks for these points. The products of digestion are absorbed into the blood, mainly in the small intestine. Simple sugars such as glucose are used to build new carbohydrates, including glycogen. Some glucose is used in respiration to release energy for cells. Amino acids are used to build new proteins, such as enzymes and structural proteins. A common slip: Saying all glucose is used only in respiration. Instead, some glucose is used to build new carbohydrates, and some is used in respiration. Exam tip: Link each product of digestion to its use: glucose to carbohydrates and respiration, amino acids to proteins, glycerol and fatty acids to lipids.

    See it

    A top-down flowchart. At the top, a node reads 'Products of digestion absorbed into the blood'. Three arrows lead down to three nodes: 'Glucose', 'Amino acids', and 'Glycerol and fatty acids'. From 'Glucose', two arrows lead to 'Build new carbohydrates, including glycogen' and 'Used in respiration to release energy'. From 'Amino acids', one arrow leads to 'Build new proteins, such as enzymes and structural proteins'. From 'Glycerol and fatty acids', one arrow leads to 'Build new lipids, including cell membranes and energy stores'. From 'Used in respiration to release energy', an arrow leads to 'Energy for synthesis', which then has arrows leading to the three building nodes: new carbohydrates, new proteins, and new lipids.
    Shows how the products of digestion absorbed into the blood are used to build new carbohydrates, proteins and lipids, with some glucose used in respiration to provide energy for synthesis.

    Key words

    Say what each word means before you turn the card.

    Absorption and transport

    Try answering aloud or in your head before turning the card.

    Synthesis of biological molecules

    Try answering aloud or in your head before turning the card.

    Cellular respiration

    Try answering aloud or in your head before turning the card.

    Energy transfer in cells

    Try answering aloud or in your head before turning the card.

    See every definition
    Absorption and transport
    The products of digestion are absorbed into the blood, mainly in the small intestine, and transported by the blood to cells.
    Synthesis of biological molecules
    The building of new carbohydrates, lipids and proteins from the products of digestion, which requires energy from respiration.
    Cellular respiration
    The process in which some glucose is used to release energy for cells.
    Energy transfer in cells
    Energy is released for cells when some glucose is used in respiration, and synthesis of new biological molecules requires this energy.

    Label the diagram

    Some boxes have lost their names. Pick the right name for each number.

    The diagram again, with 3 boxes numbered instead of named. A top-down flowchart. At the top, a node reads 'Products of digestion absorbed into the blood'. Three arrows lead down to three nodes: 'Glucose', 'Amino acids', and 'Glycerol and fatty acids'. From 'Glucose', two arrows lead to 'Build new carbohydrates, including glycogen' and 'Used in respiration to release energy'. From 'Amino acids', one arrow leads to 'Build new proteins, such as enzymes and structural proteins'. From 'Glycerol and fatty acids', one arrow leads to 'Build new lipids, including cell membranes and energy stores'. From 'Used in respiration to release energy', an arrow leads to 'Energy for synthesis', which then has arrows leading to the three building nodes: new carbohydrates, new proteins, and new lipids.

    • 1Box 1

    • 2Box 2

    • 3Box 3

    0 of 3 labelled

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